This article was writen by Duncan du Fresne, and was printed in the April 2001 issue of “Branchline”. Reprinted here with permission.
In the field of steam locomotive technology, I’m sure most would think that the advent of the American designed mechanical stoker was the major advance that led to “bigger, better, faster” ect.,coal burning steam power. NOT SO ! Oh, there’s no doubt that this device played a major role, but there’s something even more important -and it involved a Canadian, and a Canadian railway (read Canadian Pacific Railway).
CPR’s motive power engineering people were to become leaders in a development that would permit the design of fast, powerful, and EFFICIENT steam locomotives. I speak of course of the developement of the locomotive superheater, without which modern steam power as we knew it would never have taken place.
For those unfamiliar with the intricacies of steam locomotive design, let me put this technological advance in its simplest terms. The earliest steam engines, and those in “steam’s finest hour” had one thing in common: steam, under pressure from the boiler, pushed pistons in cylinders back and forth to turn driving wheels. Of course, modern steam engines were bigger and more powerful than their antique counterparts, but, as stated, they had the above basic principle in common. The newer, modern machine with it’s larger boiler, firebox, and heating surfaces, obviously produced a much greater volume of steam, and at a much higher presssure but, not so ob vious, was the higher TEMPERATURE of that steam when it got to the cylinders and was put to work.
In the modern engine, steam was (is) used in the cylinders at high temperature. Oh yes, I know the temperature of boiling water rises as the pressure in the boiler rises, but this is not the point nor will this do the job that the superheater will. We’ve got to get the temperature of the steam up around 600 degrees F so that our modern engine can work “expansively” (not expensively). In layman’s ter